"The gap between intention and effect" was what Diane Arbus said she aimed for when, facing a person, she raised her camera and clicked the shutterthe distance (at times considerable) that separates someone's self-image from the way they look to others. In a transvestite's heavy chin or the jauntily painted eyebrows of two elderly coquettes at the Automat, she found a pathos linking them to a broader humanity.

The Dutch photographer Rineke Dijkstra focuses on something a bit different: those unguarded moments when the inchoate longings and the realities of youth collide. Dijkstra, whose uncannily calm, formal portraits bear traces of Arbus's more flamboyant humanism, made her name with a series of pictures she took in the early 1990s of adolescents posed on beachfronts from Hilton Head to Odessa. There was a sociological element to this survey, a distant cousin, in its way, to August Sander's methodical documentation of Weimar society. (The slender pallor of a Polish youth, for example, brought to mind winter suppers of brown bread and cabbage.) But it was the work's emotional content that grabbed youthe exquisite ungainliness of bodies evoking a psychological vulnerability that remains, for most adults, a distant memory.

Since then, she's photographed new mothers who've just given birth, young matadors fresh from the slaughter, and soldiersa French Legionnaire and a female Israeli recruitboth before and after their inductions. The changes wrought by time upon an individual's identity, so tricky to capture in still photography, are her ever present subject. Currently on view at the Museum of Modern Art (in the exhibition Out of Time, through April 9) are pictures she took over the course of 11 years of a Bosnian immigrant to the Netherlands, a lost, dark-haired little girl in a plaid ensemble and red bow tie who is gradually transformed into a modern-looking blonde.

The 13 photographs of children and adolescents in Dijkstra's her tightly focused new show at Marian Goodman Gallery were all taken within the leafy confines of urban parks, from Amsterdam's Vondelpark (her hometown oasis) to the Amoy Botanical Garden in Xiamen, China, and including our own Prospect and Central Parks. But they are hardly portraits of leisure. The childrenlike the eerily self-assured nymphet in orange sneakers (the most exotic flower in Barcelona's Parque de la Ciudadela), who at age four or five stands with the evident pride of a conquistador on her pink scootermeet the challenge of our gaze head-on. The adolescents sit or recline, but their strained relaxation suggests contradictory energies held in check.

Take the teenage couple with crooked smiles perched on a grassy knoll in Liverpool's Sefton Park, their dirty black hair and school uniforms a bit akimbo. They resemble each other, as do people who've been married forever, though the boy's mysteriously bare feet and the girl's awkwardly turned-in toes hint at a union tinged with dementia. In another picture, a gangly Dutch youth sits in a hidden dell beside a lake, his spindly arms clasping his impossibly long legs, his ravenous teen hunger stilled by an inner watchfulness. His secrets will not be revealed to us. Dijkstra's 4 x 5" camera fixes him like a specimen, just as it captures (on another day in Vondelpark) a young girl hanging out with three friends, and every laborious nuance of her appearance: the plastic flowers on her transparent blue flip-flops, her toenails each painted a different color, the fake daisy in her hair, her artificially blue eyes, and the faint gleaming of her braces.

When she left the house that morning, did this girl's mother note each of these prophylactic adornments, props to shore up a flailing identity? Or did she pass in a blur, unseen, one more misunderstanding between generations? For beside the patches of bad skin and chewed fingernails in these pictures lies an unearthly beauty. Framed by an urban planner's vision of nature, set down amid man-made vistas, Dijkstra's youths prove there is no greater spectacle than that of their own becoming.